Method of automatically controlling the output of a carding engine



June 11, 1957 R. GIBSON ETAL 2,795,012

METHOD OF AUTOMATICALLY CONTROLLING THE OUTPUT OF A OARDING ENGINE Filed Jan. 8, 1953 United States Patent ice METHOD OF AUTOMATICALLY CONTROLLING THE OUTPUT or A CARDING ENGINE automatically controlling the production by a carding engine of slubbings, slivers, ropings or such like under Patented June 11 1957 2 tained constant, the web goes thin, leading to lighter slubbings, and when the doffer and condenser speed is reduced the speed .of the rest of the card being maintained constant, the web goes thick, leading to heavier slubbings. The method according to the present invention consists in assessing the departure of the weight per unit area of the web from a desired. value, hereafter called the deviation, by a suitable measuringdevice and causing the output from this deviee to regulate automatically the speed'of'the doifer relative to the swift or its equivalent so as to increase or decrease the thickness of the web accordinglyand thereby tend to maintain the thickness a condenser system in the woolen or other textile trades,

which broad sense the term slubbings will hereafter be used by measuring the output and adjusting it by automatically varying the speed of the doffer, relative to that of the swift. The chief object of the invention is to enable the card toproduce slubbings which are more uniform inweight per unit length than thas been previously possible, and a further object is, by relieving the carding engineer'or overlooker of the troublesome task of repeated skeining of slubbings, to give him more time to attend to'his other duties.

Other advantages which may be claimed for the invention. are (1) a yery greatreduction in the time elasping during the filling-up period following fettling before acceptable slubbings are produced, (2) a saving of productiontime and expensive raw material, since the device may also show immediately any uncontrollable departure from the desired skeins, such asmay be due to a hopper misweigh, a slipping belt, or a jammed feed, (3) elimination of the need for change wheels for the dofier/condenser drive.

Furthermore, the invention may assist in setting up the card to produce slubbings with minimum variations before the automatic control is brought into use. For this purpose the production of a permanent record or chart is'regarded as of major importance, since it allows the rapid evaluation of the effects caused by altering speeds, settings, etc., ofthe card, so enabling short term variation produced in the slubbings to be reduced, to a'minimum. This is an obvious advantage and is an essential pre-requisite if automatic control is expectedto give its best result.

It is possible for variations in slubbings controllable by this device tooriginate in the physical and/or chemical condition or treatment of the material before or during carding, including particularly the mechanical treatment and handling involved in the carding process, with the ex-.

ception of variations arising reached the carder doffen' I I 'Itis known that the weigh'per unit length of slubbings from the whole width of the card is approximately proportional to that of a few ends of slubbing taken from the centre of the card bobbins and also to the weight per unit area of the web from which they are made.

It is also known that the weight per unit area of the after the material has web can be measured by many methods, of which one.

is increased, the speed oithe restof the card being mainof the web at the desired value. It will be understood that where in this specification the context requires it, reference to the speed of the doffer applies also to the speed of the condenser or other associated mechanism or devices which are normallydriven in timed relation to the doffer. e

The method ofthe invention may also include the step of automatically making a permanent record of such web deviation as assessed by said measuring device.

The elements of the invention are (i) a measuring device, (ii) a controller, (iii) a positioner, and (iv) a variable speed transmission unit. These elements (with suitable amplifiers, switches-and power supplies) and the dofier (with its'necessary mechanical drives) constitute a closed loop automatic controlsystem.

A continuous record ofthe deviation may normally be obtained from the measuring device--by a recorder placed outside the control loop, but'it may be convenient on thegrounds of economy for the recorder to share an amplifier with a component of the control loop, e. g. the recorder and the controller mayboth be actuated by the output from the same amplifier.

The measuring device produces a signal proportional to the deviation and feeds it into the controller. In the simplest form the controller output is a constant signal (corresponding to the mean value of the dolfer speed or the set point) from which is subtracted a signal proportional to the deviation. It is desirable to subtract also an additional signal, proportional to the time integral of the-deviation. It will be understood that these signals are subtracted algebraically i. e. with due regard to the sign of the deviation.

Such a controller is described for example in British Patent No..688,464' and another is described in Instruments 26, 728. A simple transducer would be required to adapt either of these controllers to the particular form of the invention herein described, and would easily be I devised by a person skilled in the art. It is not therefore necessary to described such a transducer.

When a deviation occurs, the controller output changes, and a positioner is used to alter the setting of the control shaft of a variable ratio transmission unit through which the doffer is driven from the swift. Although the positioner may be only a sample on-off-reverse electric motor, providing floating control, it is preferred that an erroractuated position control servo-mechanism be used, maintaining constant alignment between the control shaft setting Of the variable ratio transmission unit and the output signal of the controller. The transmission ratio versus control shaftsetting relationship of the transmission unit is constant with time, hence the dofier speed can be accurately aligned with the controller output. Alternatively the doifer can drive a tachometer generator, for example, producing an output signal feeding into the servo-mechanism error detector. Any suitable form Of measuring device may be used for assessing the deviations. This might be a device for projecting through or on to the web some form of non-varying radiation as, for example, a beam of light, ultra-sonic energy, Beta rays or sound waves, and assessing the efiect of the varia-i mechanical feeler mechanism arranged to measure direct-v ly the thickness of the web.

Any suitable detectingelementcan housed in conjunction with these methods. to produce electrical cur rent variations substantially proportional to the deviation.

Since the modification of the radiation caused by the normal variations in the web weight are small as compared with the modification produced by the web as a whole, it is convenient to oppose the output of the detecting element receiving the modified radiation by the output of a seconddetecting element of the same type which is receiving radiation unmodified. by the action of the web, the output of the second element representing some function of the desired value of the web weight. In this way spurious effects due tounwanted changes in intensity of the source of radiation are: minimised.

In cases where the detecting elements are liable to .be affected by stray radiation of the same type as the de-. sired radiation, the desired radiation may be modulated in intensity and the amplifying system arranged in known manner so that only that part of the received radiation,

which is coherent with'the desired radiation is used to control the speed of the doifer and condenser.

Less dependence on .the stability of the detector and amplifier may be obtained by the use of known time sharing methods in which a single detector element is made to receive radiation alternately, first directly from the source, and second, after modification by the web, the outputs being switched so that the output produced on odd half cycles opposes that produced on even half cycles (vide Rev. Sci. Inst. 21', 203).

Alternatively, the position of a mask can be adjusted by a servo mechanism so as to intercept some of the radiation falling directly on the detector element, the density or area of the mask being a unique function of its position so that the modification of the radiation produced by the mask is made to be substantially the same as that produced by the web at any time, the position. of the mask thus becomes a measure of the web weight (vide Anal. Chem. 25, 1473).

It ispreferable to measure as wide a section of the carder web as possible to obtain an average measure which is more representative of allthe ends of slubbing being produced at a given time. For those detector elements which are normally small in size (e. g. photocells) A particular form of the invention will now be de-' scribed by wayof example ;,with reference to theaccornpanying. drawings, in which like reference numerals apply tosimilar parts and in which:

Figure l is a diagram showing schematically a sumcient portion of a woolencardingengine inside elevation i and the components of the invention, for an understand ing of the invention. The flow ofwoolerr material will be understood to take place from left to right, in the diagram.

Figure 2 is a diagram .showingin greaterde'tail the components of elementll in Figure l.

Figure3 is'a diagram of the mountings. of elements 4 and .fed through a knownmcircuit 3,designed to minimise 4 variation of the light output for any change in conditions (e. g. supply voltage variation, aging of lamp etc.).

A vacuum type photo-electric cell is mounted above the web 2 which extends between the doifer 5 of the carder part and the condenser 6 of which only the leading rollers are shown in the drawing, and a similar cell 7 is mounted below it, the rnountings'38 and 39 (Fig. 3) being such that the cells can be swung well clear of the web 2 whilst this is being initially fed to the condenser 6, and then moved exactly back into the same place for measurement.

Cell 7 is placed so that it receives light directly from substantially the same area of the source 1 as that from which the cell 4 receives it after it passes through the web 2.

The intensity of light falling on cell 4 and hence the current flowing through it is determined by the weight per unit area of the web. The current is amplified in a stable amplifier 8 and current from cell 7 is also amplified in amplifier 8, the two outputs being brought together in opposing directions in balancing circuit 9 (Figure 4). The output from this circuit feeds controller 11and recorder 10,,and isproportional to the difference in currents flowing through cells 4 and 7. Figure 4 shows the output stage of amplifier 8, the resistance network of which is balancing. circuit 9.. The numeralsr, 40 and 41 are halves of a double triode, connected as cathode rollowers. By meanswell known to the art the current through valve 40 is made proportional to that through cell 7 and the current through 41.is made proportional to that through cell 4. Potential divider resistance chain 42, 43, is the cathode load of valve 40, and is tapped by connection 44. Potentiometer is the cathode load of valve 41 and is tapped at an adjustable point by connection 46. The output is taken from connections 44 and 46, and is balanced by adjustment of the tapping point on potentiometer 45.

When the web has been brought to the correct thickness by adjusting the doffer speed by any suitable method, the tapping point on potentiometer 45 is adjusted so that the output across connections 44 and 46 is zero, and recorder 10 receives zero signal. Hence after this adjustment any change in this output is caused only by a deviation from the required value of the web thickness and is proportionalto, such deviation.

The recorder 10 may, be any one of a large, number of instruments available commercially in which a record is produced by a movable pen actuated by the outputcurrent further amplified, if necessary, drawing a line on a steadily moving chart.

For controllingvpurposes, the output current from bal' ancing circuit 9 feeds controlling unit 37, which is a 3 term electronic controller, generating proportional, integral (or .reset) and derivative .(or rate) actions about an. adjustable datum or set point. The output from this controller controls a servo-mechanism :11 (enclosed in chain line, Fig. 2) whose functionis to position the setting shaft 34 of variable ratio transmission unit 12,

so that this position is proportional to the output of controller 37. The doffer speed is proportional to the setting of this shaft. required, a discontinuous or relay servo-mechanism is preferred.

The action of servo-mechanism 11 is as follows:

The output current from controller 37 flows through a coil 18' (Fig. ,2) ofa sensitive repeater 19 (a commercially available device viz: Marchment; British Patent No. 589,423) where it reacts with the field of'a fixed permanent magnet 20,- tendingto cause-the coil 18, together with its supportingarm 31 tomove about pivot 32; The reaction is opposed by a torque supplied by spring 33, attached by one end :to the supporting-arm 31. When arm31'is displaced, it can closeeither. contact 2l or contact 22... Normally the spring torque-balances the reaction due. to the current inthe coil and neither contact is As high speed performance is not then closed. Whenthe currentfrom amplifier 9 changes the reaction changes, and either contact 21 or 22 is made, according to whether the current becomes greater or less.

Relay 23 or 24 supplied by an electrical source 25 of suitable type is then energised, relay 23 when contact 21 closes, and relay 24 when contact 22 closes. The relays operate contacts 26 or 27 as appropriate. These contacts are part of an ordinary reversing contactor 28 for electric motors, and the closing of one of these contacts causes the motor29 to be energised, bya suitable power supply 30, i. e. main supply. Normally this motor is conveniently a three phase motor, but the diagram shows the motor and contactor only diagrammatically for simplicity.

The electrical connections between contacts 21, 22 and relays 23, 24 and between relays 23, 24 and contacts 26, 27 and between 26, 27 and motor 29 are so arranged that the motor will rotate in one direction only when the output current of controller 37 increases, and will rotate in the other direction only when the controller output current decreases.

The motor 29 drives the control shaft 34 of a variable speed transmission unit 12 through a suitable mechanical drive 35 which may be gearing, belting, chain, etc., or a combination suitable to the installation. The variable transmission unit 12 has its power input shaft driven through suitable transmission by a driving wheel 15 which is itself driven by a chain etc. from the swift 16 and its power output shaft drives the dotfer 5 through a mechanical drive represented by belt, pulley and gears 14 at the controlled variable speed. Variable speed transmission unit 12 may be any one of a number of types which are commercially available, so long as it has a suitable control member such as shaft 34. Shaft 34 also drives one, 13a, of a pair of electrically connected self synchronous transmitter/repeater units (i. e. Selsyns) 13a and 131). R- tation of the rotor of the transmitter 1311 will then cause a closely similar rotation of the rotor of repeater 13b, and provided the latter is not overloaded, the two rotors will always rotate substantially through the same angle. The rotor of repeater 13b is connected by mechanical linkage 36 to the spring 33 of repeater 19, so that rotation of the shaft 34 causes the torque applied by spring 33 to arm 31 to change, tending to open the contact 21 or 22, whichever has closed. When shaft 34 has been rotated far enough, the force exerted by the spring causes contact 21 or 22 to be broken, the appropriate relays and contacts (23 or 24 and 26 or 27) are also opened or released and motor 29 comes to rest. Repeater 19 is so designed and installed as to ensure that the change of output current of controller 37 is matched by a substantially proportional rotation of shaft 34. The speed of the dofier when there is no output current from amplifier 9 may be preset by rotating shaft 34 When units 13a and 13b are not energised, or a fine adjustment may be made by adjusting the length of linkage 36 between synchro 13b and repeater 19.

In other embodiments of the invention are servomechanism 11 comprising items 18 to 33 including 13a, 13b and 36 may be replaced by known, continuously acting means, such as electronic circuits for example, giving substantially the same effects, but in a smoother manner. By mounting repeater unit 19 near the variable speed transmissions unit 12, units 13a and 13b can be replaced by a direct mechanical linkage.

Normally wheel 14 is driven through mechanical linkage 15 (i. e. through belt transmission) by the carder swift 16 and in turn, through other mechanical linkage 17 it drives the doffer and the condenser 6 together. In the illustrated embodiment of the invention, variable ratio transmission unit 12 is inserted as part of the mechanical linkage 15 enabling the speed of wheel 14 and hence of the doffer 5 and the condenser 6 together to be adjusted relative to the speed of the swift 16. If desired, however, the mechanical linkage 15 may be eliminated, being replaced by a separate local power unit (e. g. an electric motor) still driving the controlled transmission unit 12. Thus, it will be seen that, in carrying out the present method, the adjustment of the weight per unit area (i. e., thickness) of the thin web 2 by varying the speed of the doffer and the condenser 6 relative to the speed of the swift 16, is' an'essential feature of the present invention and necessary in order to automatically control the production of slubbings so as to insure the carded web and slubbings being substantially uniform. I

In an alternative method amplifier 8 may take another form such as that described in the specification of our pending British patent application No. 21,597/51. This amplifier incorporates a movable mechanical component, the displacement of which from a predetermined datum is caused to be proportional to the departure of the web weight per unit area from a desired value. In this case, as in the case when other commercial amplifiers of known design and having such a mechanical displacement as output are used, c. g. that described in British patent No. 671,389, a marking device, e. g. a pen, may be attached directly or indirectly i. e. via mechanical linkage etc. to this movable component so that it produces on a moving markable component e. g. a moving strip of paper, a record of the displacement of the movable component and hence of the departure of the weight per unit area of the web from a desired value.

The movable mechanical component can be made to close one of two contacts preferably in the form of micro switches arranged to lie one on each side of the movable component and mounted on a suitably designed moving element which is displaced linearly or in an arcuate path beneath the movable component so as to be free to follow the movable component, this moving element being linked mechanically or by electric linkage, e. g. by a self synchronous transmitter and repeater to the control shaft 34, Fig. 2 of variable speed transmission unit 12. These contacts then cause one or other of two relays to be energised which in turn actuate a commercially available reversible contactor causing a motor, conveniently of 3-phase type, to rotate in one sense or the other depending on which of the tWo contacts is closed. The motor is arranged to drive the control member 11 of variable speed transmission unit 12 so that the doifer and condenser speed are altered in the desired sense and with it the moving element carrying the contacts so that the dofier speed changes only until one or other contact is broken, whereupon the motor stops and no further change occurs until this is dictated by a further variation in web thickness causing the movable component to be displaced.

We claim:

1. The method of automatically maintaining substantially constant the weight per unit length of slubbings produced by a condenser-type carding engine having a rotary swift from which a thin film-like web of material is taken by a rotary dofier and passed to a condenser, which method comprises the steps of assessing automatically and substantially continuously during the passage of said web the variations in the weight per unit area of said web by passing a beam of light through at least a part of the width of said web, and causing the variations in the intensity of the light transmitted due to said web variations to etfect automatically corresponding variations in the speeds of the dofier and condenser together relative to the speed of the swift, said speed variations being made to correct for said web variations and so produce substantially uniform slubbings.

2. The method of automatically maintaining substantially constant the weight and thickness per unit length of slubbings produced by a condenser-type carding engine having in series a rotary swift from which a thin film-like web of material is taken by a rotary dofrer and passed to a condenser, which method comprises the steps of assessing automatically and substantially continuously during 7. the passage'of said web the variations in theweight andthickness per unit area of said web by passing a beam of light through at least part of the width of said web, and causing thevariations in the intensity of the 1ight transmitted due to said Web variations to efiect automatically 5 corresponding variations in the speeds of the doifer and condenser together relative to the speed of the swift to bring the web to the correct thickness, said speed variations being made in a sense to correct for said Web varia- 1 tions and so produce substantially uniform slubbings of 10 proper thicknesses.

UNITED STATES PATENTS King etv a1. Dec. 20, 1938 Lewis Oct 24, 1944 Rusca et a1. Apr. 5, 1949 Varga July 10, 1951 Duesberg Sept. 16, 1952 FOREIGN PATENTS France Apr. 16, 1952 

